Late Pleistocene sedimentology,taphonomy and megafauna extinction on the Darling Downs,southeastern Queensland     

G. J. Price  G. E. Webb 《Australian Journal of Earth Sciences》2013,60(6):947-970

The Kings Creek catchment, southeastern Queensland, contains a variety of Pleistocene – Holocene depositional settings. Fluvial depositional accumulation processes in the catchment reflect both high-energy channel and low-energy episodic overbank deposition. The lithofacies and depositional environments of locality QML796 were examined in detail to aid interpretation of taphonomic accumulation patterns of large and small taxa in the deposit. The basal fossiliferous unit was deposited in a meandering channel and passes upward into overbank deposits that include ephemeral interfluve channels and splays. The most striking taphonomic observations on vertebrates at the locality include: (i) low representation of post-cranial elements; (ii) high degree of bone breakage; (iii) variable abrasion with most identifiable bone elements having a low to moderate degree of abrasion; (iv) low rates of bone weathering; (v) a low degree of carnivore bone modification; and (vi) a low degree of articulated or associated specimens. Collectively, these data suggest that the material was transported into the deposit from the surrounding proximal floodplain and that the assemblages reflect substantial hydraulic sorting. However, despite that, sequential faunal horizons show a stepwise decrease in taxonomic diversity that cannot be explained by sampling or taphonomic bias. The decreasing diversity includes loss of some, but not all, megafauna and is consistent with a progressive local loss of megafauna in the catchment over an extended interval of time. Data are consistent with a climate change model for megafauna extinction but not with nearly simultaneous extinction of megafauna as required by the human-induced blitzkrieg extinction hypothesis.  相似文献   

Dynamics of fish dispersal during river-floodplain connectivity and its implications for community assembly   总被引：1，自引：0，他引：1  

Rick J. Stoffels  Rohan A. Rehwinkel  Amina E. Price  William F. Fagan 《Aquatic Sciences - Research Across Boundaries》2016,78(2):355-365

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ELF/VLF signatures of sprite-producing lightning discharges observed during the 2005 EuroSprite campaign     

E. Greenberg  C. Price  Y. Yair  C. Haldoupis  O. Chanrion  T. Neubert 《Journal of Atmospheric and Solar》2009,71(12):1254-1266

During the summer of 2005, transient luminous events were optically imaged from the French Pyrénées as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3–3000 Hz) and broadband very low frequency (VLF: 3–30 kHz) data were recorded continuously at two separate receivers in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites.The motivation for the present study was to identify the signature of the sprite-producing lightning discharges in the ELF and VLF electromagnetic frequency bands, to qualify and compare their parameters, and to study the influence of the thunderstorm-activated region on its overlaying ionosphere. For the 15 sprites analyzed, their causative positive cloud-to-ground (+CG) discharges had peak current intensities between +8 and +130 kA whereas their charge moment changes (CMC) ranged from 500 to 3500 C km. Furthermore, the peak current reported by the Météorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation with the CMCs which were estimated using ELF methods.Additionally, more than one +CG was associated with six of the sprites, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space. Finally, for a significant number of events (33%) an ELF transient was not associated with sprite occurrence, suggesting that long continuing current of tens of ms may not always be a necessary condition for sprite production, a finding which influences the estimation of the global sprite rate based on Schumann resonance (SR) measurements.  相似文献   

Oxygen in the Earth's core: a first-principles study     

Dario Alf  G. David Price  Michael J. Gillan 《Physics of the Earth and Planetary Interiors》1999,110(3-4):191-210

First-principles electronic structure calculations based on DFT have been used to study the thermodynamic, structural and transport properties of solid solutions and liquid alloys of iron and oxygen at Earth's core conditions. Aims of the work are to determine the oxygen concentration needed to account for the inferred density in the outer core, to probe the stability of the liquid against phase separation, to interpret the bonding in the liquid, and to find out whether the viscosity differs significantly from that of pure liquid iron at the same conditions. It is shown that the required concentration of oxygen is in the region 25–30 mol%, and evidence is presented for phase stability at these conditions. The Fe/O bonding is partly ionic, but with a strong covalent component. The viscosity is lower than that of pure liquid iron at Earth's core conditions. It is shown that earlier first-principles calculations indicating very large enthalpies of formation of solid solutions may need reinterpretation, since the assumed crystal structures are not the most stable at the oxygen concentration of interest.  相似文献   

Infrared space borne experiments to study Galactic structure     

Stephan D. Price 《Astrophysics and Space Science》1994,217(1-2):35-40

The Geophysics Directorate of Phillips Lab is engaged in several Galactic structure studies. These studies involve a reprocessing and analysis of the IRAS measurements and experiments on the next two infrared satellites, the Midcourse Space Experiment (MSX) and the Infrared Space Observatory (ISO). A collaboration with the Deep Near Infrared Survey (DENIS) will provide complementary coverage of the same Galactic Plane fields surveyed by MSX and ISO.  相似文献   

Electromagnetic Induction in Thin Conductors     

A. T. Price  A. A. Ashour 《Geophysical Journal International》1974,37(2):263-270

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Evidence for a low-altitude origin of lightning on Venus     

Thomas A. Croft  Gary H. Price 《Icarus》1983,53(3):548-551

Radio emissions attributed to lightning on Venus have been recorded by Venera 11 and 12 and by the Pioneer Venus Orbiter. The Venera descent records are compared to patterns of radio propagation within the Venusian atmosphere and an explanation is found for some timing trends that, if correct, indicates the lightning was below 33 km in altitude.  相似文献   

ISO-SWS Spectral Characterization of Stars     

A. M. Heras  R. F. Shipman  S. D. Price  TH. De Graauw  L. B. F. M. Waters  H. J. Walker  M. Jourdain De Muizon  M. F. Kessler  T. Prusti 《Astrophysics and Space Science》1997,255(1-2):251-253

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The geochemistry of iron and manganese in the waters and sediments of Bolstadfjord,S.W. Norway     

John Hamilton-Taylor  N.Brian Price 《Estuarine, Coastal and Shelf Science》1983,17(1):1-19

The distributions of dissolved and solid phase Fe and Mn have been variously determined in vertical profiles through the water column and sediments at three stations in Bolstadfjord, S.W. Norway. Elevated concentrations of dissolved and suspended particulate Fe and Mn are associated with restricted deep waters as a result of redox reactions and with river discharge. The basin sediments are anoxic throughout but because of the greatly restricted circulation, remobilized Fe and Mn appear to remain predominantly trapped within the fjord. Differentiation of Fe and Mn occurs to the extent that Fe sulphide precipitation is ubiquitous in the sediments whereas the entrapment of Mn, probably through Mn carbonate precipitation, is found only in the sediments of the more seaward basin (maximum Mn content of 1·5% by weight).  相似文献   

International conference on planetary satellites     

Michael J. Price 《Icarus》1974,21(3):388-398

Further analysis of visual (V) wavelength photometric function data for Saturn's ring is presented. Evidence indicating both that primary scattering dominates, and that mutual shadowing is an irrelevant concept, is reviewed. Simple anisotropic scattering radiative transfer models are used to define the probable ranges in the single scattering albedo, and in the general shape of the scattering phase function of the individual particles. Limitations on the mean perpendicular optical thickness of the ring are also obtained. Results indicate that the ring particles are highly efficient back-scatterers of visual radiation. Macroscopic particles account for the basic shape of the scattering phase function. Based on an infinite optical thickness for the ring, a minimum single scattering albedo ≈0.75 is found. Use of conservative scattering leads to a minimum optical thickness ≈0.7. The analysis is consistent with the ring particles being centimeter-size pieces of ice.  相似文献